Conventionally known is a working machine of a type having a machine body and a pair of arms mounted thereon, e.g., a stationary arm and a movable arm which is arranged for movement toward and away from the stationary arm. In order to positively clamp or crush an article to be gripped or crushed under the opening/closing motion of these arms, preferably, the direction along which the opening/closing motion plane of the arms extends must be changed in accordance with the posture of the article. For instance, when a beam or the like extending horizontally is crushed, the opening/closing plane of the arms is required to extend vertically. On the other hand, when a pillar or the like extending vertically is crushed, the plane of the arms is required to extend horizontally. For this purpose, a working machine of a type capable of changing the direction of the opening/closing plane of the arms, has already been developed as disclosed in, for example, Japanese Utility Model Publication No. Sho 57-6695.
However a further improvement is still desired in a mechanism for rotating the machine body of the working machine.